/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2005,2006,2007 INRIA

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as 

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Federico Maguolo <maguolof@dei.unipd.it>

 */

#ifndef PROPAGATION_JAKES_MODEL_H

#define PROPAGATION_JAKES_MODEL_H

#include "ns3/nstime.h"

#include "propagation-loss-model.h"

namespace ns3 {

/**

 * \brief a Jakes propagation loss model

 *

 * The Jakes propagation loss model implemented here is 

 * described in [1].

 * 

 *

 * We call path the set of rays that depart from a given 

 * transmitter and arrive to a given receiver. For each ray

 * The complex coefficient is compute as follow:

 * \f[ u(t)=u_c(t) + j u_s(t)\f]

 * \f[ u_c(t) = \frac{2}{\sqrt{N}}\sum_{n=0}^{M}a_n\cos(\omega_n t+\phi_n)\f]

 * \f[ u_s(t) = \frac{2}{\sqrt{N}}\sum_{n=0}^{M}b_n\cos(\omega_n t+\phi_n)\f]

 * where

 * \f[ a_n=\left \{ \begin{array}{ll}

 * \sqrt{2}\cos\beta_0 & n=0 \\

 * 2\cos\beta_n & n=1,2,\ldots,M

 * \end{array}

 * \right .\f]

 * \f[ b_n=\left \{ \begin{array}{ll}

 * \sqrt{2}\sin\beta_0 & n=0 \\

 * 2\sin\beta_n & n=1,2,\ldots,M

 * \end{array}

 * \right .\f]

 * \f[ \beta_n=\left \{ \begin{array}{ll}

 * \frac{\pi}{4} & n=0 \\

 * \frac{\pi n}{M} & n=1,2,\ldots,M

 * \end{array}

 * \right .\f]

 * \f[ \omega_n=\left \{ \begin{array}{ll}

 * 2\pi f_d & n=0 \\

 * 2\pi f_d \cos\frac{2\pi n}{N} & n=1,2,\ldots,M

 * \end{array}

 * \right .\f]

 *

 * The parameter \f$f_d\f$ is the doppler frequency and \f$N=4M+2\f$ where

 * \f$M\f$ is the number of oscillators per ray.

 *

 * The attenuation coefficent of the path is the magnitude of the sum of 

 * all the ray coefficients. This attenuation coefficient could be greater than

 * \f$1\f$, hence it is divide by \f$ \frac{2N_r}{\sqrt{N}} \sum_{n+0}^{M}\sqrt{a_n^2 +b_n^2}\f$

 * where \f$N_r\f$ is the number of rays.

 *

 * The initail phases \f$\phi_i\f$ are random and they are choosen according 

 * to a given distribution.

 * 

 * [1] Y. R. Zheng and C. Xiao, "Simulation Models With Correct 

 * Statistical Properties for Rayleigh Fading Channel", IEEE

 * Trans. on Communications, Vol. 51, pp 920-928, June 2003

 */

class JakesPropagationLossModel : public PropagationLossModel

{

public:

  static TypeId GetTypeId (void);

  JakesPropagationLossModel ();

  virtual ~JakesPropagationLossModel ();

  /**

   * \param nRays Number of rays per path

   *

   * Set the number of rays for each path

   */

  void SetNRays (uint8_t nRays);

  /**

   * \param nOscillators Number of oscillators

   *

   * Set the number of oscillators to use to compute the ray coefficient

   */

  void SetNOscillators (uint8_t nOscillators);

private:

  JakesPropagationLossModel (const JakesPropagationLossModel &o);

  JakesPropagationLossModel & operator = (const JakesPropagationLossModel &o);

  void DoConstruct (void);

  virtual double DoCalcRxPower (double txPowerDbm,

                                Ptr<MobilityModel> a,

                                Ptr<MobilityModel> b) const;

  class PathCoefficients;

  struct ComplexNumber {

    double real;

    double imag;

  };

  friend class PathCoefficents;

  typedef std::vector<PathCoefficients *> DestinationList;

  struct PathsSet {

    Ptr<MobilityModel> sender;

    DestinationList receivers;

  };

  typedef std::vector<PathsSet *> PathsList;

  static const double PI;

  ComplexNumber* m_amp;

  RandomVariable m_variable;

  double m_fd;  

  mutable PathsList m_paths;

  uint8_t m_nRays;

  uint8_t m_nOscillators;

};

} // namespace ns3

#endif /* PROPAGATION_JAKES_MODEL_H */