Why does 4G need to turn off when the device is connected to a Wi-Fi network?

Cristián Torres-Gluck Balmaceda June 7, 2013
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I was wondering why 4G needs to automatically disable when the device in question is connected to a Wi-Fi network. I was wondering in part out of curiosity, but also wondering if it’s for some commercial reason (i.e. for the developers/manufacturers to somehow make more money), or if it will damage the device to have both active at the same time.

As long as it doesn’t damage the device or any of its infrastructure, and if there is some benefit of doing so if at all, I would like to find out how to activate both 4G and Wi-Fi at the same time.

Device: Samsung Galaxy S III
Carrier: Verizon Wireless
Operating System: Android 4.1.2

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  1. Rob H
    June 7, 2013 at 7:22 pm

    But hang on, I can do that. I set my smartphone up as a WiFi hotspot and connect through that from my tablet computer to use the phone's data connection for internet.

    OK that's a different scenario. You are asking about when connecting the phone to a WiFi hotspot (rather than it acting as a hotspot) and using 2G/3G/4G at the same time. I guess that's simply because if you had both connections active and requested data, how would the phone "know" which to use?

    I guess you could try to have some kind of "intelligence" layer in the software that arbitrated between options - but the decision gets be too complicated - like: "use WiFi if its free but if it's paid and you have unlimited mobile data contract use mobile data but if both are paid (or capped) then use the cheaper unless close to the cap for that service... etc". You see the decision process probably needs your knowledge about the 2 types of data service available to you at any time & place.
    Also if both were active then you'd use battery faster, that's what I find when using my phone as a hotspot for the tablet.

  2. Chinmay Sarupria
    June 7, 2013 at 3:33 pm

    At a time, device can only use 1 network and it is not only with 4G. The same thing happens with 3G and 2G. If 2G or 3G network is enabled and you connect to a Wifi network you won't be able to use 2G or 3G.
    It is same as opening 2 text editors on PC and typing in both editors at the same time. When you type in one text editor the other one loses focus. The same thing happens with networks. If Wifi is enabled, you won't be able to use 4G.

    • Cristián Torres-Gluck Balmaceda
      June 8, 2013 at 9:33 pm

      Ok. That's interesting. Thanks for letting me know.

  3. ha14
    June 7, 2013 at 8:52 am

    if you shutdown 4G you will probably not able to call, mms...

    Juicedefender
    http://www.juicedefender.com/
    check if there is an option disable network data under disable on wifi

    Significantly increase your 4G Android’s battery life
    http://silverwraith.com/blog/2012/02/significantly-increase-your-4g-androids-battery-life/

    • Cristián Torres-Gluck Balmaceda
      June 8, 2013 at 9:30 pm

      I don't think you understand. My phone automatically disables 4G when it is connected to a Wi-Fi network. I've had three other smartphones before the one I have now, and they all did the same thing so I think it's normal. What I'm wondering is whether it is a technical reason (i.e. it would damage the phone if both were on at the same time), or a commercial reason (perhaps to get them to make more money or something), etc.