PositioningService.java
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package com.utbm.lo53.service;
import com.utbm.lo53.dao.HibernateDao;
import com.utbm.lo53.repository.Location;
import com.utbm.lo53.repository.RssiRecord;
import com.utbm.lo53.repository.TempRssi;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Guillaume on 09/05/2017.
*/
public class PositioningService {
private static final double DEFAULT_POSITIONING_PRECISION = 7.5;
private HibernateDao dao;
public PositioningService () {
this.dao = new HibernateDao();
}
public PositioningService (HibernateDao dao) {
this.dao = dao;
}
public Location getLocation (String clientMacAddr) {
Location bestLoc = null;
double bestLocProbability = -1;
for(Location loc : dao.getLocations()) {
//Liste des RSSISample pour une position donnée, chaque RSSISample étant
//assossié à un AccessPoint
List<RssiRecord> rssis = dao.getRssiRecord(loc.getId());
//Liste des RSSISample associé à un ap, mesuré pour un client
List<TempRssi> clientRssi = dao.getTempRssi(clientMacAddr);
double currentLocProbability = probability(clientRssi, rssis, DEFAULT_POSITIONING_PRECISION);
if(bestLocProbability == -1 || currentLocProbability > bestLocProbability){
bestLoc = loc;
bestLocProbability = currentLocProbability;
}
}
return bestLoc;
}
private double probability(List<TempRssi> temps, List<RssiRecord> rssis, double precision){
try {
double probability = 1;
for (TempRssi temp : temps) {
RssiRecord rssi = find(temp.getAp().getMac_addr(), rssis);
probability*=gauss_probability(temp.getAvg(), temp.getStdDev(), rssi.getAvg(), rssi.getStdDev(), precision);
}
return probability;
}catch(IllegalArgumentException e){
e.printStackTrace();
return -1;
}
}
private double gauss_probability(double avg1, double std1, double avg2, double std2, double precision){
final double
valDebut = Math.min(avg1-3*std1, avg2-3*std2),
valFin = Math.max(avg1+3*std1, avg2+3*std2);
double
rectDebut = valDebut,
rectFin = valDebut+precision,
probabilite = 0;
do{
probabilite+=Math.min( gauss(avg1, std1, (rectDebut+rectFin)/2), gauss(avg2, std2, (rectDebut+rectFin)/2));
rectDebut = rectFin;
rectFin+=precision;
}while(rectFin<valFin);
return probabilite;
}
private double gauss (final double avg, final double std, final double x) {
return (1/(std*Math.sqrt(2*Math.PI)))*Math.exp(-(Math.pow(x-avg, 2)/(2*Math.pow(std, 2))));
}
private RssiRecord find(String macAddr, List<RssiRecord> rrs){
final List<RssiRecord> results = new ArrayList<>();
rrs.stream().filter(rr->rr.getAp().getMac_addr().equals(macAddr)).forEach(rr->results.add(rr));
switch(results.size()){
case 0:
throw new IllegalArgumentException("No matching RssiRecord for mac address <"+macAddr+">");
case 1:
return results.get(0);
default :
throw new IllegalArgumentException("Several("+results.size()+") matching RssiRecord for mac address <"+macAddr+">");
}
}
}