WiFi over 900MHz then?
Personally, I don't like there being more licensed spectrum. I think more spectrum should be unlicensed and therefore free for all who play by the rules.
You got Zigbee and LoRaWAN for that already. IKEA has water leakage detectors (which I highly recommend, they saved my ass already), and temp/hum sensors, go for Sonoff's lineup.
But in the case of Wi-Fi specifically, part of the success story of 5 GHz (besides having much more spectrum available than 2.4 GHz and having less noisy legacy applications cluttering it) is the lower maximum EIRP in most parts of it.
This forces everybody to have smaller (and if required more) cells – which is a big win in densely populated areas such as apartment buildings, for example.
Because the cell network is designed around the towers managing resource allocation, instead of phones trying and hoping nobody else was trying at the same time. Doing it this way increases the total capacity of the network by a lot.
So to create a phone mesh network, you would effectively need to create an entire new protocol stack, probably some enhancements to the frontend/PHY for the initial connection establishment (two phones realizing they're in range of each other) and congestion handling. And depending on how you implemented it, it would be a power hog too, since listening for a tower broadcast requires much less juice than announcing your presence to the world and hoping someone is in range.
(I do actually think there is phone-to-phone communications buried somewhere in the standards, but it still requires the tower for coordination)
Apple’s AWDL is hacky and ugly in lots of ways, but has been in market for a decade or more and enables phone to phone. If WiFi forum ever gets WiFi direct 2 off the ground it could be amazing.
But phone to phone is chicken and egg; users aren’t demanding it because there aren’t any killer apps, and there aren’t any killer apps because problems like identity, privacy, resiliency haven’t been solved, and those problems haven’t been solved because users aren’t demanding these apps.
Yet the only recent movement in that area was them cutting down on AirPlay to unknown contacts, reportedly due to governmental pressure.
So unfortunately I believe that there is just no interest of Apple to make any move there, despite being in an excellent position: iMessage would solve most problems of spam, discoverability etc. (they could make it so that you can only message preexisting contacts when offline).
You ever try and have a conversation over APRS text messages without even digipeaters in a crowded urban area? Good luck getting through.
I'm not trying to save on data fees; I'd just love to do low-bandwidth peer to peer messaging with people nearby without any network around.
What if, for example, low-frequency 5G bands were available to such P2P applications as a secondary user, similarly to 5G WiFi and weather radars? If there's a network there, use that; if there isn't, do P2P!
It is however great for a non-contact point to point where you connect the xmitter and receiver by attaching adjoining faces together. Imagine a PCIe card where the edge connector had no electrical contacts it just sits in the slot and the connection is a 60GHz link between the card and the base board. With inductive power transfer you don't need any conductive contacts at all.
Its very cool and sciencey but the tranceivers are stupid expensive and the use case is really pretty limited.