BackgroundGeolocation not working in background but in foreground fire why? - geolocation

Question

Team i have implemented the tracking functionality in our app and using BackgroundGeolocation but its not working in the background below we have mentioned scenario:
Case 1:
BackgroundGeolocation is fire only 1 time if i am foreground not in background below links we have used for BackgroundGeolocation :
https://www.joshmorony.com/adding-background-geolocation-to-an-ionic-2-application/
https://www.freakyjolly.com/ionic-3-get-background-device-location-using-cordova-and-ionic-native-geolocation-plugins/
i have tried above links but i got same result for me.i really stuck location issues in ionic3 as well ionic community is not supported for any query.
loadLocation(){
// foreground Tracking
var self = this;
//get user currentLocation and update user location after move move
self.watch = this.geolocation.watchPosition(options).filter((p: any) => p.code === undefined).subscribe((position: Geoposition) => {
//self.subscription = self.watch.subscribe((position) => {
var latLng = new google.maps.LatLng(position.coords.latitude, position.coords.longitude);
console.log('lat fire1.....', +position.coords.latitude);
console.log('long fire.....', +position.coords.longitude);
//set center to map and set zoom....
self.map.setCenter(latLng);
self.map.setZoom(16);
//updateDriverLocation for get driver updated location...
self.updateDriverLocation(position.coords.latitude, position.coords.longitude);
//moveMarker for ,move marker......
self.moveMarker(position);
}, (err) => {
console.log(err);
});
// Background Tracking
let config = {
desiredAccuracy: 0,
stationaryRadius: 20,
distanceFilter: 10,
debug: true,
interval: 2000
};
this.backgroundGeolocation.configure(config).subscribe((location) => {
alert('dddddd');
console.log('BackgroundGeolocation: ' + location.latitude + ',' + location.longitude);
//updateDriverLocation for get driver updated location...
self.updateDriverLocation(location.latitude,location.longitude);
self.moveMarker(location);
}, (err) => {
console.log(err);
});
// Turn ON the background-geolocation system.
this.backgroundGeolocation.start();
}
I tried each and everything but nothing worked please team help me.