On Thu, Sep 26, 2013 at 09:20:43AM +0200, Lodewijk andré de la porte wrote: > 2013/9/26 Eugen Leitl <[email protected]> > > > 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.
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