Yeah, this part threw me off: > The system would work on a low frequency, 13.5 gigahertz, enabling it to penetrate dust, smoke, rain, bushes, trees, and even walls.

This relatively high freq would be a poor penetrator of anything wouldn't it? And with high power usage to boot. Unless I'm missing something here

I think they mean “relatively” low frequency. Militaries stick to higher frequency bands to ostensibly make it harder for non-state actors and non-peer foes to use or modify COTS equipment or build their own to intercept it.

But yeah, even 13.5ghz would be subject to interference. Though the 35+ ghz the other companies are looking at sound even worse. They must know something we don’t, I think

Perhaps those freqs allow more compact beamforming? Putting aside that I'm not privy to those companies' research I would bet on LoRa (or another sub-GHz low power modulation technique) coupled with crypto coprocessors. Super low-cost (crypto chip being the majority of the BOM), very long range (over 10km in open ares), highly secure. One downside would be low bitrate (.3 ~ 30kbits/s). With a worst case of maximum range and spread factor, even 37 bytes should be enough to trade unique signatures