gr::digital::constellation Class Reference

An abstracted constellation object. More...

#include <gnuradio/digital/constellation.h>

Inheritance diagram for gr::digital::constellation:

Public Member Functions
	constellation (std::vector< gr_complex > constell, std::vector< int > pre_diff_code, unsigned int rotational_symmetry, unsigned int dimensionality)
	constellation ()
virtual	~constellation ()
void	map_to_points (unsigned int value, gr_complex *points)
	Returns the constellation points for a symbol value. More...
std::vector< gr_complex >	map_to_points_v (unsigned int value)
virtual unsigned int	decision_maker (const gr_complex *sample)=0
	Returns the constellation point that matches best. More...
unsigned int	decision_maker_v (std::vector< gr_complex > sample)
	Takes a vector rather than a pointer. Better for SWIG wrapping. More...
unsigned int	decision_maker_pe (const gr_complex *sample, float *phase_error)
	Also calculates the phase error. More...
virtual void	calc_metric (const gr_complex *sample, float *metric, gr::digital::trellis_metric_type_t type)
	Calculates distance. More...
virtual void	calc_euclidean_metric (const gr_complex *sample, float *metric)
virtual void	calc_hard_symbol_metric (const gr_complex *sample, float *metric)
std::vector< gr_complex >	points ()
	Returns the set of points in this constellation. More...
std::vector< gr_complex >	s_points ()
	Returns the vector of points in this constellation. Raise error if dimensionality is not one. More...
std::vector< std::vector < gr_complex > >	v_points ()
	Returns a vector of vectors of points. More...
bool	apply_pre_diff_code ()
	Whether to apply an encoding before doing differential encoding. (e.g. gray coding) More...
void	set_pre_diff_code (bool a)
	Whether to apply an encoding before doing differential encoding. (e.g. gray coding) More...
std::vector< int >	pre_diff_code ()
	Returns the encoding to apply before differential encoding. More...
unsigned int	rotational_symmetry ()
	Returns the order of rotational symmetry. More...
unsigned int	dimensionality ()
	Returns the number of complex numbers in a single symbol. More...
unsigned int	bits_per_symbol ()
unsigned int	arity ()
constellation_sptr	base ()
pmt::pmt_t	as_pmt ()
void	gen_soft_dec_lut (int precision, float npwr=1.0)
	Generates the soft decision LUT based on constellation and symbol map. More...
virtual std::vector< float >	calc_soft_dec (gr_complex sample, float npwr=1.0)
	Calculate soft decisions for the given sample. More...
void	set_soft_dec_lut (const std::vector< std::vector< float > > &soft_dec_lut, int precision)
	Define a soft decision look-up table. More...
bool	has_soft_dec_lut ()
	Returns True if the soft decision LUT has been defined, False otherwise. More...
std::vector< float >	soft_decision_maker (gr_complex sample)
	Returns the soft decisions for the given sample. More...

Protected Member Functions
float	get_distance (unsigned int index, const gr_complex *sample)
unsigned int	get_closest_point (const gr_complex *sample)
void	calc_arity ()
void	max_min_axes ()

Protected Attributes
std::vector< gr_complex >	d_constellation
std::vector< int >	d_pre_diff_code
bool	d_apply_pre_diff_code
unsigned int	d_rotational_symmetry
unsigned int	d_dimensionality
unsigned int	d_arity
float	d_scalefactor
	The factor by which the user given constellation points were scaled by to achieve an average amplitude of 1. More...
float	d_re_min
float	d_re_max
float	d_im_min
float	d_im_max
std::vector< std::vector< float > >	d_soft_dec_lut
int	d_lut_precision
float	d_lut_scale

Detailed Description

An abstracted constellation object.

The constellation objects hold the necessary information to pass around constellation information for modulators and demodulators. These objects contain the mapping between the bits and the constellation points used to represent them as well as methods for slicing the symbol space. Various implementations are possible for efficiency and ease of use.

Standard constellations (BPSK, QPSK, QAM, etc) can be inherited from this class and overloaded to perform optimized slicing and constellation mappings.

Constructor & Destructor Documentation

gr::digital::constellation::constellation	(	std::vector< gr_complex >	constell,
		std::vector< int >	pre_diff_code,
		unsigned int	rotational_symmetry,
		unsigned int	dimensionality
	)

gr::digital::constellation::constellation

(

)

virtual gr::digital::constellation::~constellation ( )

virtual

Member Function Documentation

bool gr::digital::constellation::apply_pre_diff_code ( )

inline

Whether to apply an encoding before doing differential encoding. (e.g. gray coding)

unsigned int gr::digital::constellation::arity ( )

inline

pmt::pmt_t gr::digital::constellation::as_pmt ( )

inline

References pmt::make_any().

constellation_sptr gr::digital::constellation::base ( )

inline

unsigned int gr::digital::constellation::bits_per_symbol ( )

inline

void gr::digital::constellation::calc_arity ( )

protected

virtual void gr::digital::constellation::calc_euclidean_metric ( const gr_complex *  sample, float *  metric  )

virtual

virtual void gr::digital::constellation::calc_hard_symbol_metric ( const gr_complex *  sample, float *  metric  )

virtual

virtual void gr::digital::constellation::calc_metric ( const gr_complex *  sample, float *  metric, gr::digital::trellis_metric_type_t  type  )

virtual

Calculates distance.

Calculates metrics for all points in the constellation. For use with the viterbi algorithm.

virtual std::vector<float> gr::digital::constellation::calc_soft_dec ( gr_complex  sample, float  npwr = 1.0  )

virtual

Calculate soft decisions for the given sample.

Calculate the soft decisions from the given sample at the given noise power npwr.

This is a very costly algorithm (especially for higher order modulations) and should be used sparingly. It uses the gen_soft_dec_lut function to generate the LUT, which should be done once or if a large change in the noise floor is detected.

Instead of using this function, generate the LUT using the gen_soft_dec_lut after creating the constellation object and then use the soft_decision_maker function to return the answer from the LUT.

Parameters

sample	The complex sample to get the soft decisions.
npwr	Estimate of the noise power (if known).

virtual unsigned int gr::digital::constellation::decision_maker ( const gr_complex *  sample )

pure virtual

Returns the constellation point that matches best.

Implemented in gr::digital::constellation_8psk, gr::digital::constellation_dqpsk, gr::digital::constellation_qpsk, gr::digital::constellation_bpsk, gr::digital::constellation_sector, and gr::digital::constellation_calcdist.

unsigned int gr::digital::constellation::decision_maker_pe	(	const gr_complex *	sample,
		float *	phase_error
	)

Also calculates the phase error.

unsigned int gr::digital::constellation::decision_maker_v

(

std::vector< gr_complex >

sample

)

Takes a vector rather than a pointer. Better for SWIG wrapping.

unsigned int gr::digital::constellation::dimensionality ( )

inline

Returns the number of complex numbers in a single symbol.

void gr::digital::constellation::gen_soft_dec_lut	(	int	precision,
		float	npwr = 1.0
	)

Generates the soft decision LUT based on constellation and symbol map.

Generates the soft decision LUT based on constellation and symbol map. It can be given a estimate of the noise power in the channel as npwr.

Parameters

precision	Number of bits of precision on each axis.
npwr	Estimate of the noise power (if known).

This is expensive to compute.

unsigned int gr::digital::constellation::get_closest_point ( const gr_complex *  sample )

protected

float gr::digital::constellation::get_distance ( unsigned int  index, const gr_complex *  sample  )

protected

bool gr::digital::constellation::has_soft_dec_lut

(

)

Returns True if the soft decision LUT has been defined, False otherwise.

void gr::digital::constellation::map_to_points	(	unsigned int	value,
		gr_complex *	points
	)

Returns the constellation points for a symbol value.

std::vector<gr_complex> gr::digital::constellation::map_to_points_v

(

unsigned int

value

)

void gr::digital::constellation::max_min_axes ( )

protected

std::vector<gr_complex> gr::digital::constellation::points ( )

inline

Returns the set of points in this constellation.

std::vector<int> gr::digital::constellation::pre_diff_code ( )

inline

Returns the encoding to apply before differential encoding.

unsigned int gr::digital::constellation::rotational_symmetry ( )

inline

Returns the order of rotational symmetry.

std::vector<gr_complex> gr::digital::constellation::s_points

(

)

Returns the vector of points in this constellation. Raise error if dimensionality is not one.

void gr::digital::constellation::set_pre_diff_code ( bool  a )

inline

Whether to apply an encoding before doing differential encoding. (e.g. gray coding)

void gr::digital::constellation::set_soft_dec_lut	(	const std::vector< std::vector< float > > &	soft_dec_lut,
		int	precision
	)

Define a soft decision look-up table.

Define a soft decision look-up table (LUT). Because soft decisions can be calculated in various ways with various levels of accuracy and complexity, this function allows users to create a LUT in their own way.

Setting the LUT here means that has_soft_dec_lut will return true. Decision vectors returned by soft_decision_maker will be calculated using this LUT.

Parameters

soft_dec_lut	The soft decision LUT as a vector of tuples (vectors in C++) of soft decisions. Each element of the LUT is a vector of k-bit floats (where there are k bits/sample in the constellation).
precision	The number of bits of precision used when generating the LUT.

std::vector<float> gr::digital::constellation::soft_decision_maker

(

gr_complex

sample

)

Returns the soft decisions for the given sample.

Returns the soft decisions for the given sample. If a LUT is defined for the object, the decisions will be calculated from there. Otherwise, this function will call calc_soft_dec directly to calculate the soft decisions.

Parameters

sample

The complex sample to get the soft decisions.

std::vector<std::vector<gr_complex> > gr::digital::constellation::v_points

(

)

Returns a vector of vectors of points.

Member Data Documentation

bool gr::digital::constellation::d_apply_pre_diff_code

protected

unsigned int gr::digital::constellation::d_arity

protected

std::vector<gr_complex> gr::digital::constellation::d_constellation

protected

unsigned int gr::digital::constellation::d_dimensionality

protected

float gr::digital::constellation::d_im_max

protected

float gr::digital::constellation::d_im_min

protected

int gr::digital::constellation::d_lut_precision

protected

float gr::digital::constellation::d_lut_scale

protected

std::vector<int> gr::digital::constellation::d_pre_diff_code

protected

float gr::digital::constellation::d_re_max

protected

float gr::digital::constellation::d_re_min

protected

unsigned int gr::digital::constellation::d_rotational_symmetry

protected

float gr::digital::constellation::d_scalefactor

protected

The factor by which the user given constellation points were scaled by to achieve an average amplitude of 1.

std::vector< std::vector<float> > gr::digital::constellation::d_soft_dec_lut

protected

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

• constellation.h