Right now LTE is the fastest standard as far as mobile internet connectivity is concerned. Of course you speeds will vary depending on your country and also depending on how congested the Network is, but as it stands, it is the fastest. However it is obvious that we can’t use LTE forever, which is why many are looking at 5G as the next step forward.
The good news for AT&T customers is that the carrier has recently announced that they will start getting ready to test their own 5G network. This shouldn’t really come as a surprise especially since last September, Verizon announced that they will also be testing 5G networks, so obviously AT&T has no desire to be left behind.
AT&T is expected to work with Ericsson and Intel for the equipment necessary to test the network, which they are aiming for the summer over in their Austin, Texas labs. In fact Qualcomm has recently announced a new X16 LTE radio which seems like it would be suitable for 5G use.