Is there any physical limitation to cell carries sharing the same frequency?

Question

Currently in the U.S. certain companies are granted leases on certain frequencies for cell phone communication. I was discussing with a friend how this allows a company with a lower frequency to get a physical advantage over another cell service company that may only have the option to lease a higher frequency. (For building penetration and distance of transmission)

Ignoring the engineering problem of revamping their systems, are there any physical limitation to opening up the leases and allowing all the major carriers to operate on the same band/frequency?

Answer 1

If two adjacent cells share the same frequency, they will interfere with each other.

Generally, frequencies are reused in non-adjacent cells, to give a chance for the distance to attenuate the unwanted signals to a manageable level of interference.

With proper design of signals (OFDM, with cyclic prefixes to mitigate multipath), you can achieve an SFN, Single Frequency Network.

Answer 2

I've realized the intense wish (among RF students in recent years, even the last decade) to explore MIMO ---- multiple-input-multiple-output ---- antennas, is the local generation of

phased-array systems

for communication at the local/router/cellsite/home communication-links.

With the tracking of where each subscriber in the service area of a cellsite, with the plenteous compute power to craft each RF emission at each of the numerous antennas atop those cell-towers [by manipulating the I+Q energy of EACH CHANNEL], the cellsite can beam energy at each handset.

The cellsite can beam energy at each handset.

Additionally, reversing the behavior, the cellsite can compute how to peak the synthesized-rf-antenna-pattern response to each handset, even as the handset moves, and the cellsite can direct nulling-responses at co-channel interferers of other cellsites.

IMHO