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Comment by njoubert | Hacker News Reader

I think you are hugely overestimating the importance of non-line-of-sight communication.

Your example is cell phone communication. That is not the intended use case of this technology. Facebook's laser comms is part of their Aquila project, attempting to build a network of drones to supply internet.

This application works just fine with a line-of-sight constraint. At 50,000ft just about everything is line of sight.

Anyone building backhand RF links also hugely care about line-of-sight. Microwave towers carrying multi-gigabit speeds are carefully arranged for line of sight: this much improves reliability and throughput.

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Yes, if they are thinking about deploying vertically to a LEO satellite then perhaps LoS is not an issue unless you are indoors. But if you want to require the user install an antenna or receiver outdoors then it can work, but again, the atmospheric loss can be an issue, for example if it is cloudy outdoors then light will have difficulty getting through that. Some wavelengths may be better than others but anyone who has had satellite TV knows what happens when it rains. But I do think what they are doing is interesting and has a long term promise for a lot of use cases.

Yeah, was going to say something similar. UHF/VHF don't have "line of sight" but if I've got a hill between me and someone else I'm sure as hell going to have a hard time hearing him.

They put repeaters up on tall areas for that reason. Same with cell towers, yes you can get through non-dense material but there's still a signal loss associated with it.

The effect detailed in this comment and its parent is the Fresnel Zone [1], which isn't quite direct, human intuition 'line-of-sight', but that concept applied to RF waves.

Essentially, any object intruding into a blimp-shaped region between the receiver and the transmitter has the potential to mess things up, and is corrected by having a payload in the signal that's tolerant or self-correcting of errors.

[1] https://en.wikipedia.org/wiki/Fresnel_zone

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