GNU Radio Manual and C++ API Reference  3.7.9.2
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gr::digital::constellation Class Referenceabstract

An abstracted constellation object. More...

#include <gnuradio/digital/constellation.h>

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_complexmap_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_complexpoints ()
 Returns the set of points in this constellation. More...
 
std::vector< gr_complexs_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< std::vector< float > > soft_dec_lut ()
 
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_complexd_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
sampleThe complex sample to get the soft decisions.
npwrEstimate of the noise power (if known).
virtual unsigned int gr::digital::constellation::decision_maker ( const gr_complex sample)
pure virtual
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
precisionNumber of bits of precision on each axis.
npwrEstimate 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_lutThe 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).
precisionThe number of bits of precision used when generating the LUT.
std::vector< std::vector<float> > gr::digital::constellation::soft_dec_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
sampleThe 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

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