It might sound impossible to do, but it can indeed be known. And of course there are advantages and disadvantages when you do it. But this feature is not available for all versions of Android, and can only be enjoyed starting from Android 9 (Pie) and above.
Its performance does not combine the connection between WiFi and Cellular Data, but will choose one of them. So for example WiFi does not have internet access, it will automatically be routed to cellular data quickly.
Turning on WiFi or Cellular Data manually sometimes takes a long time, until it takes a few seconds. But by activating both, you can switch quickly without having to wait anymore.
Oh yes, this feature is hidden on Android phones. So you have to activate
Developer Mode first to be able to start following the method below. Please read the article first How to enable Developer Mode on Android 4.0 and above
If Developer Mode has been activated, please follow the steps below:
How To Use WiFi and Cellular Data Simultaneously on Android
1. Open Settings in Your Phone.
2. Scroll down and tap the menu Developer Choices or Developer Mode.
3. Scroll down again and activate the options Quota Always Active.
4. Now try to turn on WiFi and Cellular Data, surely both can be used together.
Now switching networks from WiFi to Cellular Data or vice versa will be very fast and no longer need to wait. It is suitable when playing games, to choose a stable and fast network.
Advantages and Disadvantages for Using WiFi and Cellular Data in Simultaneously on Android
In short, the advantage of using two networks simultaneously is that you can switch internet connections quickly, so when one network is deactivated, the system will immediately use the other network that is still alive.
While the drawback is that users cannot distinguish whether they are currently using WiFi or Cellular Data unless they are using an assistance application, such as a speed meter. In addition, activating the two networks simultaneously also impacts on battery power which is a bit wasteful.
For that, please think first to activate this feature. Or you can also activate it only when playing online games, it's worth it.