How to impliment Push Notification functionality with Ionic and Crosswalk?

Hello guys, i’m building a Telecommunication app using SIP.JS library, and i have some notifications, like chat message, or receiving a call, i want to impliment push notifications when the user is not on the app, should receive a notification ?

So you could checkout this post about push notifications.

http://devgirl.org/2014/12/16/push-notifications-sample-app-with-ionic-and-ngcordova/