pulse_shape.h

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#ifndef PULSE_SHAPE_H
#define PULSE_SHAPE_H

#include <itpp/base/vec.h>
#include <itpp/base/matfunc.h>
#include <itpp/base/math/trig_hyp.h>
#include <itpp/signal/filter.h>
#include <itpp/signal/resampling.h>


namespace itpp
{

template<class T1, class T2, class T3>
class Pulse_Shape
{
public:
  Pulse_Shape();
  Pulse_Shape(const Vec<T2> &impulse_response, int upsampling_factor);
  virtual ~Pulse_Shape() {}
  void set_pulse_shape(const Vec<T2> &impulse_response, int upsampling_factor);
  Vec<T2> get_pulse_shape(void) const;
  int get_upsampling_factor() const;
  int get_pulse_length() const;
  int get_filter_length() const;

  void shape_symbols(const Vec<T1> &input, Vec<T3> &output);
  Vec<T3> shape_symbols(const Vec<T1> &input);

  void shape_samples(const Vec<T1> &input, Vec<T3> &output);
  Vec<T3> shape_samples(const Vec<T1> &input);

  void clear(void);

protected:
  Vec<T2> impulse_response;
  MA_Filter<T1, T2, T3> shaping_filter;
  int pulse_length;
  int upsampling_factor;
  bool setup_done;
};

template<class T1>
class Raised_Cosine : public Pulse_Shape<T1, double, T1>
{
public:
  Raised_Cosine() {}
  Raised_Cosine(double roll_off, int filter_length = 6, int upsampling_factor = 8);
  virtual ~Raised_Cosine() {}
  void set_pulse_shape(double roll_off_factor, int filter_length = 6, int upsampling_factor = 8);
  double get_roll_off(void) const;

protected:
  double roll_off_factor;
};

template<class T1>
class Root_Raised_Cosine : public Pulse_Shape<T1, double, T1>
{
public:
  Root_Raised_Cosine() {}
  Root_Raised_Cosine(double roll_off_factor, int filter_length = 6, int upsampling_factor = 8);
  virtual ~Root_Raised_Cosine() {}
  void set_pulse_shape(double roll_off_factor, int filter_length = 6, int upsampling_factor = 8);
  double get_roll_off(void) const;

protected:
  double roll_off_factor;
};

//-------------------------------------------------------------------------
// Implementation of templated code starts here
//-------------------------------------------------------------------------

//---------------------------- Pulse_Shape --------------------------------

template<class T1, class T2, class T3>
Pulse_Shape<T1, T2, T3>::Pulse_Shape()
{
  setup_done = false;
  pulse_length = 0;
  upsampling_factor = 0;
}


template<class T1, class T2, class T3>
Pulse_Shape<T1, T2, T3>::Pulse_Shape(const Vec<T2> &impulse_response, int upsampling_factor)
{
  set_pulse_shape(impulse_response, upsampling_factor);
}

template<class T1, class T2, class T3>
void Pulse_Shape<T1, T2, T3>::set_pulse_shape(const Vec<T2> &impulse_response_in, int upsampling_factor_in)
{
  it_error_if(impulse_response_in.size() == 0, "Pulse_Shape: impulse response is zero length");
  it_error_if(upsampling_factor_in < 1, "Pulse_Shape: incorrect upsampling factor");

  pulse_length = (impulse_response_in.size() - 1) / upsampling_factor_in;
  upsampling_factor = upsampling_factor_in;

  impulse_response = impulse_response_in;
  shaping_filter.set_coeffs(impulse_response);
  shaping_filter.clear();
  setup_done = true;
}

template<class T1, class T2, class T3>
Vec<T2> Pulse_Shape<T1, T2, T3>::get_pulse_shape(void) const
{
  return impulse_response;
}

template<class T1, class T2, class T3>
int Pulse_Shape<T1, T2, T3>::get_upsampling_factor(void) const
{
  return upsampling_factor;
}

template<class T1, class T2, class T3>
int Pulse_Shape<T1, T2, T3>::get_pulse_length(void) const
{
  return pulse_length;
}

template<class T1, class T2, class T3>
int Pulse_Shape<T1, T2, T3>::get_filter_length(void) const
{
  return impulse_response.size();
}

template<class T1, class T2, class T3>
void Pulse_Shape<T1, T2, T3>::shape_symbols(const Vec<T1>& input, Vec<T3> &output)
{
  it_assert(setup_done, "Pulse_Shape must be set up before using");
  it_error_if(pulse_length == 0, "Pulse_Shape: impulse response is zero length");
  it_error_if(input.size() == 0, "Pulse_Shape: input is zero length");

  if (upsampling_factor > 1)
    output = shaping_filter(upsample(input, upsampling_factor));
  else
    output = input;
}

template<class T1, class T2, class T3>
Vec<T3> Pulse_Shape<T1, T2, T3>::shape_symbols(const Vec<T1>& input)
{
  it_assert(setup_done, "Pulse_Shape must be set up before using");
  Vec<T3> temp;
  shape_symbols(input, temp);
  return temp;
}

template<class T1, class T2, class T3>
void Pulse_Shape<T1, T2, T3>::shape_samples(const Vec<T1>& input, Vec<T3> &output)
{
  it_assert(setup_done, "Pulse_Shape must be set up before using");
  it_error_if(pulse_length == 0, "Pulse_Shape: impulse response is zero length");
  it_error_if(input.size() == 0, "Pulse_Shape: input is zero length");

  if (upsampling_factor > 1)
    output = shaping_filter(input);
  else
    output = input;
}

template<class T1, class T2, class T3>
Vec<T3> Pulse_Shape<T1, T2, T3>::shape_samples(const Vec<T1>& input)
{
  it_assert(setup_done, "Pulse_Shape must be set up before using");
  Vec<T3> temp;
  shape_samples(input, temp);
  return temp;
}

template<class T1, class T2, class T3>
void Pulse_Shape<T1, T2, T3>::clear(void)
{
  it_assert(setup_done, "Pulse_Shape must be set up before using");
  shaping_filter.clear();
}

//-------------------- Raised_Cosine -----------------------------------

template<class T1>
Raised_Cosine<T1>::Raised_Cosine(double roll_off_factor, int filter_length, int upsampling_factor)
{
  set_pulse_shape(roll_off_factor, filter_length, upsampling_factor);
}

template<class T1>
void Raised_Cosine<T1>::set_pulse_shape(double roll_off_factor_in, int filter_length, int upsampling_factor_in)
{
  it_error_if(roll_off_factor_in < 0 || roll_off_factor_in > 1, "Raised_Cosine: roll-off out of range");
  roll_off_factor = roll_off_factor_in;

  it_assert(is_even(filter_length), "Raised_Cosine: Filter length not even");

  int i;
  double t, den;
  this->upsampling_factor = upsampling_factor_in;
  this->pulse_length = filter_length;
  this->impulse_response.set_size(filter_length * upsampling_factor_in + 1,
                                  false);

  for (i = 0; i < this->impulse_response.size(); i++) {
    // delayed to be casual
    t = (double)(i - filter_length * upsampling_factor_in / 2)
        / upsampling_factor_in;
    den = 1 - sqr(2 * roll_off_factor * t);
    if (den == 0) {
      // exception according to "The Care and feeding of digital,
      // pulse-shaping filters" by Ken Gentile,
      // the limit of raised cosine impulse responce function,
      // as (alpha * t / tau) approaches (+- 0.5) is given as:
      this->impulse_response(i) = sinc(t) * pi / 4;
    }
    else {
      this->impulse_response(i) = std::cos(roll_off_factor * pi * t)
                                  * sinc(t) / den;
    }
  }

  // BUGFIX: Commented out to achieve similar results to Matlab
  // rcosfil function. Now the concatenation of two root-raised
  // cosine filters gives tha same results as a one raised cosine
  // shaping function.
  // this->impulse_response /= std::sqrt(double(this->upsampling_factor));
  this->shaping_filter.set_coeffs(this->impulse_response);
  this->shaping_filter.clear();
  this->setup_done = true;
}

template<class T1>
double Raised_Cosine<T1>::get_roll_off(void) const
{
  it_assert(this->setup_done, "Pulse_Shape must be set up before using");
  return roll_off_factor;
}

//-------------------- Root_Raised_Cosine -----------------------------------

template<class T1>
Root_Raised_Cosine<T1>::Root_Raised_Cosine(double roll_off_factor, int filter_length, int upsampling_factor)
{
  set_pulse_shape(roll_off_factor, filter_length, upsampling_factor);
}

template<class T1>
void Root_Raised_Cosine<T1>::set_pulse_shape(double roll_off_factor_in, int filter_length, int upsampling_factor_in)
{
  it_error_if(roll_off_factor_in <= 0 || roll_off_factor_in > 1,
              "Root_Raised_Cosine: roll-off out of range");
  roll_off_factor = roll_off_factor_in;

  it_assert(is_even(filter_length),
            "Root_Raised_Cosine: Filter length not even");

  int i;
  double t, num, den, tmp_arg;
  this->upsampling_factor = upsampling_factor_in;
  this->pulse_length = filter_length;
  this->impulse_response.set_size(filter_length * upsampling_factor_in + 1,
                                  false);

  for (i = 0; i < this->impulse_response.size(); i++) {
    // delayed to be casual
    t = (double)(i - filter_length * upsampling_factor_in / 2)
        / upsampling_factor_in;
    den = 1 - sqr(4 * roll_off_factor * t);
    if (t == 0) {
      this->impulse_response(i) = 1 + (4 * roll_off_factor / pi)
                                  - roll_off_factor;
    }
    else if (den == 0) {
      tmp_arg = pi / (4 * roll_off_factor);
      this->impulse_response(i) = roll_off_factor / std::sqrt(2.0)
                                  * ((1 + 2 / pi) * std::sin(tmp_arg) + (1 - 2 / pi) * std::cos(tmp_arg));
    }
    else {
      num = std::sin(pi * (1 - roll_off_factor) * t)
            + std::cos(pi * (1 + roll_off_factor) * t) * 4 * roll_off_factor * t;
      this->impulse_response(i) = num / (pi * t * den);
    }
  }

  this->impulse_response /= std::sqrt(double(upsampling_factor_in));
  this->shaping_filter.set_coeffs(this->impulse_response);
  this->shaping_filter.clear();
  this->setup_done = true;
}

template<class T1>
double Root_Raised_Cosine<T1>::get_roll_off(void) const
{
  it_assert(this->setup_done, "Pulse_Shape must be set up before using");
  return roll_off_factor;
}


// ----------------------------------------------------------------------
// Instantiations
// ----------------------------------------------------------------------

ITPP_EXPORT_TEMPLATE template class ITPP_EXPORT Pulse_Shape<double, double, double>;
ITPP_EXPORT_TEMPLATE template class ITPP_EXPORT Pulse_Shape < std::complex<double>, double,
  std::complex<double> >;
ITPP_EXPORT_TEMPLATE template class ITPP_EXPORT Pulse_Shape < std::complex<double>, std::complex<double>,
  std::complex<double> >;

ITPP_EXPORT_TEMPLATE template class ITPP_EXPORT Root_Raised_Cosine<double>;
ITPP_EXPORT_TEMPLATE template class ITPP_EXPORT Root_Raised_Cosine<std::complex<double> >;

ITPP_EXPORT_TEMPLATE template class ITPP_EXPORT Raised_Cosine<double>;
ITPP_EXPORT_TEMPLATE template class ITPP_EXPORT Raised_Cosine<std::complex<double> >;


} // namespace itpp

#endif // #ifndef PULSE_SHAPE_H