Interesting question. Very few, if any, could have foreseen where we would be today, let's say 50 years ago in 1964. But I think we might be better equipped to approach the question going forward.
How much data do we need local access to? For instance, would it even be desirable to have all financial transactions in the world, on a real time basis, go through our personal mobile device? It would need to be a very powerful mobile device to make use of such enormous quantities of data. I'm sure we could find more efficient ways to get the desired results.
The real question is how much unique information could be available to a mobile device that would be useful to transmit? These could include biomentric information, precise location and orientation information and various user inputs like voice, camera, keyboard etc. And what information needs to be received to present, control, or otherwise be useful.
Another is that each mobile device, or other categories, could be a peer to peer part of some sort of mesh type network. But even here, maybe especially, each node would carry a small part of aggrigate traffic.
I believe the future will bring better understanding of how much data personal mobile devices need and there will be a useful limit, not defined by RF capability but by utility.
28 or 39 GHz will not work in all scenerios but will in many. Beam forming will be key at both the mobile end and at the base station. Also terrain mapping for reflective surfaces in urban environments as well as attenuation factors through walls.
The mobile device will need higher accuracy location mechanisms and orientation info to report to base stations so beam forming will be colabrative effort.
Seemless handoff of course, not only geography, including obstructions but bands too.
Rick, how is 5G defined? 4G is 1 Gb/s throughput for stationary links I think, what is the corresponding number for 5G? and why do we need 5G? isn't 1 Gb/s enough? do we need to watch HD movies on msart phones? Kris