Geolocation Service stops when App goes in background after several minutes

Hi,

I use the following geolocation service code for android devices to track user location continually :

Ti.App.Properties.setBool("service_running", true);
 
Ti.API.info("Starting geoloc ...");
geolocation();
Ti.API.info("Ending geoloc ...");
 
Ti.App.Properties.setBool("service_running", false);
 
function geolocation(){
 
    Titanium.Geolocation.Android.manualMode = true;
 
    var _gpsProvider = Ti.Geolocation.Android.createLocationProvider( {
      name : Ti.Geolocation.PROVIDER_GPS,//,
      minUpdateTime:5, // Max location events per given seconds
    } );
 
    Ti.Geolocation.Android.addLocationProvider( _gpsProvider );
    Ti.Geolocation.pauseLocationUpdateAutomatically = false;
    Ti.Geolocation.addEventListener('location', function(e) {
      createNotification('Geolocalisation running ...', "....", "...");
      if (!e.success || e.error) {
        Ti.API.info(e.error);
        //alert('error ' + JSON.stringify(e.error));
        return;
      }
      Ti.API.info(e.coords);
      var longitude = e.coords.longitude;
      var latitude = e.coords.latitude;
      var time= +new Date();
      coords.push(time+"@"+longitude+"@"+latitude);
      //alert(apikey);
      if(Ti.Network.online && apikey != "") {
            // Sending geoloc data to web server ...
      }
    });
}

Any idea why ? How can I be sure that even if application is in background, user keeps getting tracked, I need to keep geolocation running while user did not decide to stop definitively the app (even though I know it will drain battery - the purpose is to have a full time tracking app).

Thank you in advance for your time :)