source: proiecte/ptvs/src/vnsim/network/propagation/Shadowing.java @ 31

/************************************************************************************
 * Copyright (C) 2008 by Politehnica University of Bucharest and Rutgers University
 * All rights reserved.
 * Refer to LICENSE for terms and conditions of use.
 ***********************************************************************************/
//Petroaca - shadowing propagation model class ; it receives the parameters from the transmitter and it calculates the received power
package vnsim.network.propagation;


import java.util.*;

import vnsim.map.object.Globals;


public class Shadowing
{
        //distance at which the reference power received is calcualted
        private static double referenceDistance=Globals.REFERENCE_DISTANCE;
        
        private static double pathLossExp=Globals.PATH_LOSS_EXPONENT_URBAN;
        
        private static double shadowingDeviation=Globals.SHADOWING_DEVIATION;
        
        private static long seed=Globals.RANDOM_SEED;
        
        private static Random randVar=new Random(seed);
        
        //returns the received power of the frame in DBm 
        public static double getPr(double Pt,double R,boolean withObstruction)
        {
                if(Pt<=0.0 || R<=0.0)
                        return -1;
                
                if(withObstruction)
                        pathLossExp=Globals.PATH_LOSS_EXPONENT_URBAN;
                else
                        pathLossExp=Globals.PATH_LOSS_EXPONENT_FREE;
                
                //calculate the receiving power at reference distance
                double Pr0=FreeSpace.getPr(Pt,referenceDistance);
                
                //calculate average power loss predicted by path loss model
                double averageP= -10.0 * pathLossExp * Math.log10(R/referenceDistance);
                
                //get the power loss by adding a random variable
                double powerLoss= averageP + randVar.nextDouble()*shadowingDeviation;
                
                //calculate the received power
                double Pr= Pr0 * Math.pow(10.0, powerLoss/10.0);
                
                return Pr;
                
        }
}