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 po

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