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I'm thinking about getting a Verizon Android 4G phone. But I have a question about how 4G works...

4G is supported in my city, however if I move into a part of the city where 4G isn't covered or it's spotty, does the phone degrade to 3G service (assuming that is available)? Or does it degrade all the way down to normal slow cell service (the same service you get when 3G isn't available)?

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2 Answers 2

up vote 9 down vote accepted

I will say yes, but, that answer doesn't necessarily hold true 100% of the time. It really depends on the bands that the device supports.

On the device spec sheets you will usually see something like this:

800/1900/700

These are the bands that the device will operate on. I pulled these numbers from the Droid Bionic. From that spec sheet, it goes even further and shows that it supports EV-DO rev.A (CDMA/3G), and LTE (4G). So this phone does support Verizon's 3G & 4G networks, which means that if 4G is not avaialble, then it will fall back to the CDMA data network (which is what the device will uses for Voice even when data uses LTE.

The same rules apply for GSM networks like AT&T and T-Mobile. The device spec sheet will say what bands the device can operate on, and if the carrier's network operates within that band, then the phone will work. This is why iPhone users can use unlocked AT&T iPhones on T-Mobile's network, but they only can get EDGE data. This is because the iPhone does not support the band that T-mobile uses for its UMTS/HSPA/HSPA+ (3G/4G) data networks.

T-mobile bands:

  • 850/1900 (GSM/GPRS/EDGE)
  • 1700/2100 (UMTS/HSPA)

AT&T bands:

  • 850/1900 (GSM/GPRS/EDGE)
  • 580/1900 (UMTS/HSPA) (3G)
  • 700 (LTE) (4G)

Verizon bands:

  • 800/1900 (CMDA/EV-DO) (3G)
  • 700 (LTE) (4G)

Sprint doesn't know if they want to use LTE or WiMax so I am not listing their bands.

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Yep. You're pretty much guaranteed that any "4G" phone from carrier X will work on carrier X's 3G network. Until 4G coverage is ubiquitous it would be suicide for a carrier to do otherwise. –  Matthew Read Oct 20 '11 at 20:46

Yes, the current Verizon 4G phones all have support for the 3G network. As Matthew Read points out, it would not make sense until 4G coverage is available everywhere that 3G is.

If you have an active data connection, your phone will get a new IP address when it lands on the new network (4G->3G or 3G->4G); apps must be able to handle this event (any app that can handle a temporary loss of data on a 3G network should be fine here)

This document from Motorola's developer site includes the following description:

"As the connected device moves from cell to cell, it tries to maintain its network connection. It will generally be successful if the network type doesn’t change between cells. However, if the device moves into or out of the 4G coverage area, the data connection will be dropped and your IP address will change. Because this can happen while an app has an active data connection open, Android sends an android.net.ConnectivityManager.CONNECTIVITY_ACTION broadcast whenever there is a change in the network. If your app needs to be aware of network changes, register for this broadcast. "

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