Its on by default. The devices ship with CDMA/LTE set as the default.
If your not picking up 4G LTE then chances are your not in an are with it.
Very few markets have it, and the ones that do are still being built out..
There is no 4G on GS3 like IAmSixNine mentioned. This is an LTE and the 4G comes on ONLY when you're in the LTE coverage area. Otherwise, you're gonna be in 3G mode all the time. However, the 3G coverage is not bad for the modem that this phone has.
i believe the SIII came pre set to CDMA only..the LTEVO on the other hand was shipped with the LTE/CDMA already picked...not really sure why other than the market isnt really fully deployed...but at what point has any manufacturer put extra effort into their phones before they launch them? lol
This is true, however it's always a good idea to disable LTE mode if you are not an LTE area. This means turning your device to CDMA only. This will ensure that your device isn't constantly switching between modes in order to function.
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one of the newer phones came with it switched to CDMA only..i cant remember which one it was though.
then again this might have changed since there are actually areas with LTE now..