/* -*-  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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

 */

#ifndef PROPAGATION_LOSS_MODEL_H

#define PROPAGATION_LOSS_MODEL_H

#include "ns3/object.h"

namespace ns3 {

class MobilityModel;

/**

 * \brief Modelize the propagation loss through a transmission medium

 *

 * Calculate the receive power (dbm) from a transmit power (dbm),

 * and, a mobility model for the source and destination positions.

 */

class PropagationLossModel : public Object

{

public:

  virtual ~PropagationLossModel ();

  /**

   * \param txPowerDbm the tx power

   * \param a the mobility model of the source

   * \param b the mobility model of the destination

   * \returns the receive power (dbm)

   */

  virtual double GetRxPower (double txPowerDbm,

			     Ptr<MobilityModel> a,

			     Ptr<MobilityModel> b) const = 0;

  /**

   * \returns the default propagation loss model as specified

   * by \valueref{PropagationLossModelType}.

   */

  static Ptr<PropagationLossModel> CreateDefault (void);

};

/**

 * \brief The propagation loss is random

 */ 

class RandomPropagationLossModel : public PropagationLossModel

{

public:

  /**

   * Use the default parameters from \valueref{RandomPropagationLossDistribution}.

   */

  RandomPropagationLossModel ();

  /**

   * \param variable the RandomVariable to use for this

   * instance.

   */

  RandomPropagationLossModel (const RandomVariable &variable);

  virtual ~RandomPropagationLossModel ();

  virtual double GetRxPower (double txPowerDbm,

			     Ptr<MobilityModel> a,

			     Ptr<MobilityModel> b) const;

private:

};

/**

 * \brief a Friis propagation loss model

 *

 * The Friis propagation loss model was first described in

 * "A Note on a Simple Transmission Formula", by 

 * "Harald T. Friis".

 * 

 * The original equation was described as:

 *  \f$ \frac{P_r}{P_t} = \frac{A_r A_t}{d^2\lambda^2} \f$

 *  with the following equation for the case of an

 *  isotropic antenna with no heat loss:

 *  \f$ A_{isotr.} = \frac{\lambda^2}{4\pi} \f$

 *

 * The final equation becomes:

 * \f$ \frac{P_r}{P_t} = \frac{\lambda^2}{(4 \pi d)^2} \f$

 *

 * Modern extensions to this original equation are:

 * \f$ P_r = \frac{P_t G_t G_r \lambda^2}{(4 \pi d)^2 L}\f$

 *

 * With:

 *  - \f$ P_r \f$ : reception power (W)

 *  - \f$ P_t \f$ : transmission power (W)

 *  - \f$ G_t \f$ : transmission gain (unit-less)

 *  - \f$ G_r \f$ : reception gain (unit-less)

 *  - \f$ \lambda \f$ : wavelength (m)

 *  - \f$ d \f$ : distance (m)

 *  - \f$ L \f$ : system loss (unit-less)

 *

 *

 * This model is invalid for small distance values.

 * The current implementation returns the txpower as the rxpower

 * for any distance smaller than \valueref{FriisPropagationLossMinDistance}.

 */

class FriisPropagationLossModel : public PropagationLossModel

{

public:

  /**

   * Use the default parameters from \valueref{FriisPropagationLossLambda},

   * \valueref{FriisPropagationLossSystemLoss}, and,

   * \valueref{FriisPropagationLossMinDistance}.

   */

  FriisPropagationLossModel ();

  /**

   * \param frequency (Hz)

   * \param speed (m/s)

   *

   * Set the main wavelength used in the Friis model 

   * calculation.

   */

  void SetLambda (double frequency, double speed);

  /**

   * \param lambda (m) the wavelength

   *

   * Set the main wavelength used in the Friis model 

   * calculation.

   */

  void SetLambda (double lambda);

  /**

   * \param systemLoss (dimension-less)

   *

   * Set the system loss used by the Friis propagation model.

   */

  void SetSystemLoss (double systemLoss);

  /**

   * \param minDistance the minimum distance

   *

   * Below this distance, the txpower is returned

   * unmodified as the rxpower.

   */

  void SetMinDistance (double minDistance);

  /**

   * \returns the current wavelength (m)

   */

  double GetLambda (void) const;

  /**

   * \returns the current system loss (dimention-less)

   */

  double GetSystemLoss (void) const;

  virtual double GetRxPower (double txPowerDbm,

			     Ptr<MobilityModel> a,

			     Ptr<MobilityModel> b) const;

private:

  double DbmToW (double dbm) const;

  double DbmFromW (double w) const;

  static const double PI;

  double m_lambda;

  double m_systemLoss;

  double m_minDistance;

};

/**

 * \brief a log distance propagation model.

 *

 * This model calculates the reception power with a so-called

 * log-distance propagation model:

 * \f$ L = L_0 + 10 n log_{10}(\frac{d}{d_0})\f$

 *

 * where:

 *  - \f$ n \f$ : the path loss distance exponent

 *  - \f$ d_0 \f$ : reference distance (m)

 *  - \f$ L_0 \f$ : path loss at reference distance (dB)

 *  - \f$ d \f$ : distance (m)

 *  - \f$ L \f$ : path loss (dB)

 *

 * When the path loss is requested at a distance smaller than

 * the reference distance, the tx power is returned.

 *

 */

class LogDistancePropagationLossModel : public PropagationLossModel

{

public:

  /**

   * Use the default parameters from

   * \valueref{LogDistancePropagationLossExponent}, and,

   * \valueref{LogDistancePropagationLossReferenceType}

   * to create a new propagation loss model.

   */

  LogDistancePropagationLossModel ();

  /**

   * \param n the path loss exponent.

   * Set the path loss exponent.

   */

  void SetPathLossExponent (double n);

  /** 

   * \returns the current path loss exponent.

   */

  double GetPathLossExponent (void) const;

  /**

   * \param model the reference propagation model

   */

  void SetReferenceModel (Ptr<PropagationLossModel> model);

  void SetReferenceDistance (double referenceDistance);

  virtual double GetRxPower (double txPowerDbm,

			     Ptr<MobilityModel> a,

			     Ptr<MobilityModel> b) const;

private:

  static Ptr<PropagationLossModel> CreateDefaultReference (void);

  double m_exponent;

  double m_referenceDistance;

  Ptr<PropagationLossModel> m_reference;

};

} // namespace ns3

#endif /* PROPAGATION_LOSS_MODEL_H */