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itpp::Root_Raised_Cosine< T1 > Class Template Reference

(Square) Root Raised Cosine (RRC) Pulse Shaper More...

#include <itpp/comm/pulse_shape.h>

Inheritance diagram for itpp::Root_Raised_Cosine< T1 >:
itpp::Pulse_Shape< T1, double, T1 >

Public Member Functions

 Root_Raised_Cosine ()
 Constructor.
 
 Root_Raised_Cosine (double roll_off_factor, int filter_length=6, int upsampling_factor=8)
 Constructor.
 
virtual ~Root_Raised_Cosine ()
 Destructor.
 
void set_pulse_shape (double roll_off_factor, int filter_length=6, int upsampling_factor=8)
 Set pulse_shape, roll_off_factor between 0 and 1, filter_length even.
 
double get_roll_off (void) const
 Get the Roll-off factor.
 
void set_pulse_shape (const Vec< double > &impulse_response, int upsampling_factor)
 Set the general impulse response of the FIR filter.
 
Vec< doubleget_pulse_shape (void) const
 Get the pulse shape.
 
int get_upsampling_factor () const
 Get the over sampling factor.
 
int get_pulse_length () const
 Get the length of the pulse in number of symbols.
 
int get_filter_length () const
 Get the length of the internal FIR filter.
 
void shape_symbols (const Vec< T1 > &input, Vec< T1 > &output)
 Shape the input symbols performing upsampling.
 
Vec< T1shape_symbols (const Vec< T1 > &input)
 Shape the input symbols performing upsampling.
 
void shape_samples (const Vec< T1 > &input, Vec< T1 > &output)
 Shape the input samples already upsampled.
 
Vec< T1shape_samples (const Vec< T1 > &input)
 Shape the input symbols already upsampled.
 
void clear (void)
 Clear internal states.
 

Protected Attributes

double roll_off_factor
 The roll off factor (i.e. alpha)
 
Vec< doubleimpulse_response
 The impulse resounse of the pulse shaping filter.
 
MA_Filter< T1, double, T1shaping_filter
 The pulse shaping filter.
 
int pulse_length
 Length in symbols.
 
int upsampling_factor
 Samples per input symbol.
 
bool setup_done
 Ensures that setup is called before any other member function.
 

Detailed Description

template<class T1>
class itpp::Root_Raised_Cosine< T1 >

(Square) Root Raised Cosine (RRC) Pulse Shaper

Upsamples and shapes symbols as square root raised cosine pulses with a given roll-off factor $ \alpha $ (zero is not allowed

It is called square root raised cosine since it is defined as the square root of the raised cosine pulse in the frequency domain. Thus with a transmitter pulse shape of root raised cosine and a receiver filter that is root raised cosine, the overall response will be a raised cosine.

For more details see e.g. Lee & Messerschmitt, p. 228. Observe that the shaping is done with a FIR filter where the size is given by filter_length * over_sample_factor + 1. The first samples in the output will therefore be zero or small before the memory of the filter is filled.

What is important, when using RRC shaping in a transmission system with the AWGN channel, the mean power of the output samples is not normalised, so the channel noise variance (or shaped signal) should be scaled appropriately.

The class is templated as follows: T1 is the type of the input and the output samples. An example of usage is:

#include "itpp/itcomm.h"
BPSK bpsk;
vec symbols, samples;
symbols = bpsk.modulate_bits(randb(20));
samples = rrc.shape_symbols(symbols);
General array class.
Definition array.h:105
BPSK modulator with real symbols.
Definition modulator.h:877
void modulate_bits(const bvec &bits, vec &output) const
Modulate bits into BPSK symbols in complex domain.
bin randb(void)
Generates a random bit (equally likely 0s and 1s)
Definition random.h:793
Include file for the IT++ communications module.

Definition at line 226 of file pulse_shape.h.

Constructor & Destructor Documentation

◆ Root_Raised_Cosine() [1/2]

template<class T1 >
itpp::Root_Raised_Cosine< T1 >::Root_Raised_Cosine ( )
inline

Constructor.

Definition at line 230 of file pulse_shape.h.

◆ Root_Raised_Cosine() [2/2]

template<class T1 >
itpp::Root_Raised_Cosine< T1 >::Root_Raised_Cosine ( double  roll_off_factor,
int  filter_length = 6,
int  upsampling_factor = 8 
)

Constructor.

Definition at line 417 of file pulse_shape.h.

◆ ~Root_Raised_Cosine()

template<class T1 >
virtual itpp::Root_Raised_Cosine< T1 >::~Root_Raised_Cosine ( )
inlinevirtual

Destructor.

Definition at line 234 of file pulse_shape.h.

Member Function Documentation

◆ set_pulse_shape() [1/2]

template<class T1 >
void itpp::Root_Raised_Cosine< T1 >::set_pulse_shape ( double  roll_off_factor,
int  filter_length = 6,
int  upsampling_factor = 8 
)

Set pulse_shape, roll_off_factor between 0 and 1, filter_length even.

Definition at line 423 of file pulse_shape.h.

References itpp::is_even(), it_assert, it_error_if, itpp::pi, itpp::Array< T >::set_size(), itpp::Array< T >::size(), and itpp::sqr().

◆ get_roll_off()

template<class T1 >
double itpp::Root_Raised_Cosine< T1 >::get_roll_off ( void  ) const

Get the Roll-off factor.

Definition at line 467 of file pulse_shape.h.

References it_assert.

◆ set_pulse_shape() [2/2]

void itpp::Pulse_Shape< T1, double , T1 >::set_pulse_shape ( const Vec< double > &  impulse_response,
int  upsampling_factor 
)
inherited

Set the general impulse response of the FIR filter.

Observe that the pulse shape must have a duration of an integer number of symbols. Thus the length of the impulse response-1 modulo over sampling is an integer.

Definition at line 89 of file pulse_shape.h.

◆ get_pulse_shape()

Vec< double > itpp::Pulse_Shape< T1, double , T1 >::get_pulse_shape ( void  ) const
inherited

Get the pulse shape.

Definition at line 91 of file pulse_shape.h.

◆ get_upsampling_factor()

int itpp::Pulse_Shape< T1, double , T1 >::get_upsampling_factor ( void  ) const
inherited

Get the over sampling factor.

Definition at line 93 of file pulse_shape.h.

◆ get_pulse_length()

int itpp::Pulse_Shape< T1, double , T1 >::get_pulse_length ( void  ) const
inherited

Get the length of the pulse in number of symbols.

Definition at line 95 of file pulse_shape.h.

◆ get_filter_length()

int itpp::Pulse_Shape< T1, double , T1 >::get_filter_length ( void  ) const
inherited

Get the length of the internal FIR filter.

Definition at line 97 of file pulse_shape.h.

◆ shape_symbols() [1/2]

void itpp::Pulse_Shape< T1, double , T1 >::shape_symbols ( const Vec< T1 > &  input,
Vec< T1 > &  output 
)
inherited

Shape the input symbols performing upsampling.

Definition at line 100 of file pulse_shape.h.

◆ shape_symbols() [2/2]

Vec< T1 > itpp::Pulse_Shape< T1, double , T1 >::shape_symbols ( const Vec< T1 > &  input)
inherited

Shape the input symbols performing upsampling.

Definition at line 102 of file pulse_shape.h.

◆ shape_samples() [1/2]

void itpp::Pulse_Shape< T1, double , T1 >::shape_samples ( const Vec< T1 > &  input,
Vec< T1 > &  output 
)
inherited

Shape the input samples already upsampled.

Definition at line 105 of file pulse_shape.h.

◆ shape_samples() [2/2]

Vec< T1 > itpp::Pulse_Shape< T1, double , T1 >::shape_samples ( const Vec< T1 > &  input)
inherited

Shape the input symbols already upsampled.

Definition at line 107 of file pulse_shape.h.

◆ clear()

void itpp::Pulse_Shape< T1, double , T1 >::clear ( void  )
inherited

Clear internal states.

Definition at line 110 of file pulse_shape.h.

Member Data Documentation

◆ roll_off_factor

template<class T1 >
double itpp::Root_Raised_Cosine< T1 >::roll_off_factor
protected

The roll off factor (i.e. alpha)

Definition at line 242 of file pulse_shape.h.

◆ impulse_response

Vec<double > itpp::Pulse_Shape< T1, double , T1 >::impulse_response
protectedinherited

The impulse resounse of the pulse shaping filter.

Definition at line 114 of file pulse_shape.h.

◆ shaping_filter

MA_Filter<T1, double , T1 > itpp::Pulse_Shape< T1, double , T1 >::shaping_filter
protectedinherited

The pulse shaping filter.

Definition at line 116 of file pulse_shape.h.

◆ pulse_length

int itpp::Pulse_Shape< T1, double , T1 >::pulse_length
protectedinherited

Length in symbols.

Definition at line 118 of file pulse_shape.h.

◆ upsampling_factor

int itpp::Pulse_Shape< T1, double , T1 >::upsampling_factor
protectedinherited

Samples per input symbol.

Definition at line 120 of file pulse_shape.h.

◆ setup_done

bool itpp::Pulse_Shape< T1, double , T1 >::setup_done
protectedinherited

Ensures that setup is called before any other member function.

Definition at line 122 of file pulse_shape.h.


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

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