On Thu, Sep 26, 2013 at 09:20:43AM +0200, Lodewijk andré de la porte wrote:
2013/9/26 Eugen Leitl <eugen@leitl.org>
It's really hard to jam the sky, especially in VIS range.
"Huh. Guys, what's that on our radio scanner? Someone calls us?"
They want to pick up a parabolic dish, a LoS laser or a phased array tracking a point source overhead, all sending at maybe 5-10 W power? Sure, if your sky is thick with mapping drones. Sounds like a fifth world problem.
Hard to jam, easy to trace. Even regular Dutch police forces have triangulation tactics to find pirate radio stations.
Isotropic radiators with high power are easy to spot. Dynamic tight beams need at least a passing point of alignment to get a position fix on the ground station. NSA sigint used that microwave LoS interception, but this wouldn't scale for millions of users and very brief low-power bursts during random alignment events.
This is where I'm more enthusiastic about near-optical connections. A laser, invisible spectrum ofc, and a small black surface (iow:detector) are all it takes. It will still be visible (at night) with special hardware. Street lanterns (depending on the type) might make them invisible at night too. Bandwidth is wonderful, and there's plenty of spectrum to duplicate bandwidth too. Quite like fiber, except for the ideal transmission.
Or maybe you just buy http://www.ubnt.com/airfiber or the lower-grade gear for LoS.
And that highlights the problems. You have to keep the laser pointed, that means not diffracted by thermic differences or blocked by dust and other particles (like, you know, leaves). This might be less trouble than it'd seem at first, and even better it can be automated by a lens system.
A just graduated ship's lieutenant laughed at me for suggesting laser communication as the future. "No spying, very high speed, very wide bandwidth!" and he effectively answered "Line of sight, irreliable, no need for speed and just use satellite".
A yagi pointed skywards should be hidable inside the house, so I guess he's somewhat right.
Phased arrays which are flat or half domes are compact and don't look like anything from air. If you're clever, you can integrate these into a PV panel.